# How to find separation point over airfoil

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April 10, 2013, 10:36
How to find separation point over airfoil
#1
New Member

Leo
Join Date: Jan 2013
Location: Duisburg,Germany
Posts: 3
Rep Power: 6
Dear all,

I'm relatively new to OpenFOAM and as a part of my MSc-thesis I am trying to simulate flow field over a naca arifoil in OpenFOAM.

Now I'm having trouble to find where is the flow separation point in my simulation. I'm working with a 2D geometry.
I have got some useful information here and done some work: I modified the simpleFoam solver in OpenFOAM to get the velocity gradient or pressure gradient, but I can not figure out where is my mistake to get the good result.

This is what I have modified from simpleFoam solver(in red color) and I have compiled the modified solver after the change.
createFields.H
Quote:
Here is the detail: naca0015 airfoil, simpleFoam solver , kOmegaSST model
0 folder:

U
Quote:
 /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class volVectorField; object U; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 1 -1 0 0 0 0]; internalField uniform (0.9848 0.1736 0); boundaryField { inlet { type fixedValue; value \$internalField; } outlet { type inletOutlet; inletValue uniform (0 0 0); value \$internalField; } "airfoil.*" { type fixedValue; value uniform (0 0 0); } defaultFaces { type empty; } } //
p
Quote:
 FoamFile { version 2.0; format ascii; class volScalarField; object p; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -2 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0; } "airfoil.*" { type zeroGradient; } defaultFaces { type empty; } } // ************************************************** *********************** //
omega
Quote:
 FoamFile { version 2.0; format ascii; class volScalarField; location "0"; object omega; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 0 -1 0 0 0 0]; internalField uniform 9.8; boundaryField { inlet { type fixedValue; value uniform 9.8; } outlet { type inletOutlet; inletValue uniform 9.8; value uniform 9.8; } airfoil { type omegaWallFunction; Cmu 0.09; kappa 0.41; E 9.8; beta1 0.075; value uniform 9.8; } defaultFaces { type empty; } } // ************************************************** *********************** //
nut
Quote:
 FoamFile { version 2.0; format ascii; class volScalarField; location "0"; object nut; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -1 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type calculated; value uniform 0; } outlet { type calculated; value uniform 0; } airfoil { type nutkWallFunction; Cmu 0.09; kappa 0.41; E 9.8; value uniform 0; } defaultFaces { type empty; } } // ************************************************** *********************** //
k
Quote:
 FoamFile { version 2.0; format ascii; class volScalarField; location "0"; object k; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -2 0 0 0 0]; internalField uniform 0.00375; boundaryField { inlet { type fixedValue; value uniform 0.00375; } outlet { type inletOutlet; inletValue uniform 0.00375; value uniform 0.00375; } airfoil { type kqRWallFunction; value uniform 0.00375; } defaultFaces { type empty; } } // ************************************************** *********************** //
blockMeshDict
Quote:
 /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1.00; vertices ( ( -4.700000 0.0000 0.00 ) //Pt 0 ( -2.342151 -4.2449 0.00 ) //Pt 1 ( 5.055282 -1.5451 0.00 ) //Pt 2 ( 5.055282 1.5451 0.00 ) //Pt 3 ( -2.342151 4.2449 0.00 ) //Pt 4 ( 0.300000 0.0750 0.00 ) //Pt 5 ( 0.000000 0.0000 0.00 ) //Pt 6 ( 0.300000 -0.0750 0.00 ) //Pt 7 ( 0.900000 -0.0181 0.00 ) //Pt 8 ( 0.900000 0.0181 0.00 ) //Pt 9 ( -4.700000 0.0000 0.10 ) //Pt 10 ( -2.342151 -4.2449 0.10 ) //Pt 11 ( 5.055282 -1.5451 0.10 ) //Pt 12 ( 5.055282 1.5451 0.10 ) //Pt 13 ( -2.342151 4.2449 0.10 ) //Pt 14 ( 0.300000 0.0750 0.10 ) //Pt 15 ( 0.000000 0.0000 0.10 ) //Pt 16 ( 0.300000 -0.0750 0.10 ) //Pt 17 ( 0.900000 -0.0181 0.10 ) //Pt 18 ( 0.900000 0.0181 0.10 ) //Pt 19 ); blocks ( hex ( 0 1 7 6 10 11 17 16) ( 26 50 1) simpleGrading ( 10.0000 0.0010 1) hex ( 1 2 8 7 11 12 18 17) ( 49 50 1) simpleGrading ( 0.1000 0.0010 1) hex ( 2 3 9 8 12 13 19 18) ( 80 50 1) simpleGrading ( 1.0000 0.0010 1) hex ( 3 4 5 9 13 14 15 19) ( 49 50 1) simpleGrading ( 10.0000 0.0010 1) hex ( 4 0 6 5 14 10 16 15) ( 26 50 1) simpleGrading ( 0.1000 0.0010 1) ); edges ( polyLine 6 7 ( ( 0.0125 -0.0237 0.0000 ) ( 0.0250 -0.0327 0.0000 ) ( 0.0500 -0.0444 0.0000 ) ( 0.0750 -0.0525 0.0000 ) ( 0.1000 -0.0585 0.0000 ) ( 0.1500 -0.0668 0.0000 ) ( 0.2000 -0.0717 0.0000 ) ( 0.2500 -0.0743 0.0000 ) ) polyLine 16 17 ( ( 0.0125 -0.0237 0.1000 ) ( 0.0250 -0.0327 0.1000 ) ( 0.0500 -0.0444 0.1000 ) ( 0.0750 -0.0525 0.1000 ) ( 0.1000 -0.0585 0.1000 ) ( 0.1500 -0.0668 0.1000 ) ( 0.2000 -0.0717 0.1000 ) ( 0.2500 -0.0743 0.1000 ) ) polyLine 7 8 ( ( 0.4000 -0.0725 0.0000 ) ( 0.5000 -0.0662 0.0000 ) ( 0.6000 -0.0570 0.0000 ) ( 0.7000 -0.0458 0.0000 ) ( 0.8000 -0.0328 0.0000 ) ) polyLine 17 18 ( ( 0.4000 -0.0725 0.1000 ) ( 0.5000 -0.0662 0.1000 ) ( 0.6000 -0.0570 0.1000 ) ( 0.7000 -0.0458 0.1000 ) ( 0.8000 -0.0328 0.1000 ) ) polyLine 9 8 ( ( 1.0000 0.0016 0.0000 ) ) // trailing edge polyLine 19 18 ( ( 1.0000 -0.0016 0.1000 ) ) // trailing edge polyLine 9 5 ( ( 0.8000 0.0328 0.0000 ) ( 0.7000 0.0458 0.0000 ) ( 0.6000 0.0570 0.0000 ) ( 0.5000 0.0662 0.0000 ) ( 0.4000 0.0725 0.0000 ) ) polyLine 19 15 ( ( 0.8000 0.0328 0.1000 ) ( 0.7000 0.0458 0.1000 ) ( 0.6000 0.0570 0.1000 ) ( 0.5000 0.0662 0.1000 ) ( 0.4000 0.0725 0.1000 ) ) polyLine 5 6 ( ( 0.2500 0.0743 0.0000 ) ( 0.2000 0.0717 0.0000 ) ( 0.1500 0.0668 0.0000 ) ( 0.1000 0.0585 0.0000 ) ( 0.0750 0.0525 0.0000 ) ( 0.0500 0.0444 0.0000 ) ( 0.0250 0.0327 0.0000 ) ( 0.0125 0.0237 0.0000 ) ) polyLine 15 16 ( ( 0.2500 0.0743 0.1000 ) ( 0.2000 0.0717 0.1000 ) ( 0.1500 0.0668 0.1000 ) ( 0.1000 0.0585 0.1000 ) ( 0.0750 0.0525 0.1000 ) ( 0.0500 0.0444 0.1000 ) ( 0.0250 0.0327 0.1000 ) ( 0.0125 0.0237 0.1000 ) ) arc 0 1 (-4.070970 -2.427885 0.000000 ) arc 10 11 (-4.070970 -2.427885 0.100000 ) arc 1 2 ( 0.300000 -5.000000 0.000000 ) arc 11 12 ( 0.300000 -5.000000 0.100000 ) arc 2 3 ( 5.300000 0.000000 0.000000 ) arc 12 13 ( 5.300000 0.000000 0.100000 ) arc 3 4 ( 0.300000 5.000000 0.000000 ) arc 13 14 ( 0.300000 5.000000 0.100000 ) arc 4 0 (-4.070970 2.427885 0.000000 ) arc 14 10 (-4.070970 2.427885 0.100000 ) polyLine 4 5 ( ( 0.3000 0.3875 0.0000 ) ) polyLine 14 15 ( ( 0.3000 0.3875 0.1000 ) ) polyLine 1 7 ( ( 0.3000 -0.3875 0.0000 ) ) polyLine 11 17 ( ( 0.3000 -0.3875 0.1000 ) ) polyLine 9 3 ( ( 0.9614 0.1473 0.0000 ) ) // trailing edge polyLine 19 13 ( ( 0.9614 0.1473 0.1000 ) ) // trailing edge polyLine 8 2 ( ( 0.9614 -0.1473 0.0000 ) ) // trailing edge polyLine 18 12 ( ( 0.9614 -0.1473 0.1000 ) ) // trailing edge ); patches ( patch inlet ( ( 4 14 10 0 ) ( 0 10 11 1 ) ) patch outlet ( ( 1 11 12 2 ) ( 2 12 13 3 ) ( 3 13 14 4 ) ) wall airfoil ( ( 5 15 16 6 ) ( 6 16 17 7 ) ( 7 17 18 8 ) ( 8 18 19 9 ) ( 9 19 15 5 ) ) ); mergePatchPairs ( ); //* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Any help would be MUCH appreciated!

Best regards
Leo
Attached Files
 RASProperties.txt (950 Bytes, 5 views) transportProperties.txt (944 Bytes, 2 views) controlDict.txt (1.8 KB, 5 views) fvSchemes.txt (1.4 KB, 5 views) fvSolution.txt (2.3 KB, 4 views)

Last edited by oscarli; April 11, 2013 at 04:26.

 April 10, 2013, 11:44 #2 Senior Member   Fumiya Nozaki Join Date: Jun 2010 Location: Yokohama, Japan Posts: 217 Blog Entries: 1 Rep Power: 11 The wall shear stress vanishes at separation points and you can calculate the wall shear stress using wallShearStress utility. The thread (http://www.cfd-online.com/Forums/ope...omponents.html) could be of help. Hope this helps, Fumiya

April 12, 2013, 03:25
#3
New Member

Leo
Join Date: Jan 2013
Location: Duisburg,Germany
Posts: 3
Rep Power: 6
Hi Fumiya,

Thank you very much for your reply. I will try the wallShearStress utility.

Quote:
 Originally Posted by fumiya The wall shear stress vanishes at separation points and you can calculate the wall shear stress using wallShearStress utility. The thread (http://www.cfd-online.com/Forums/ope...omponents.html) could be of help. Hope this helps, Fumiya

April 12, 2013, 05:08
#4
New Member

Leo
Join Date: Jan 2013
Location: Duisburg,Germany
Posts: 3
Rep Power: 6
Hi Fumiya,

I'v got something seems good. Is that right? I'v put the results in attach files.
Thank you very much.
Attached Images
 sp.jpg (12.4 KB, 132 views) sp1.jpg (14.9 KB, 118 views)

 Tags pressure gradient, separation point, velocity gradient

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